1. Field of the Invention
This invention relates to capacitor ignition systems and more particularly to ignition systems for internal combustion engines including devices with windings on iron cores and associated circuit components charge a capacitor from a the field of a rotating magnet and subsequently discharge the capacitor to develop a high ignition voltage. The system of the invention has excellent performance characteritics and it is efficient and highly reliable and trouble-free in operation while being readily and economically manufacurable.
2. Background of the Prior Art
There are a number of disclosures in the prior art of capacitor ignition systems which charge a capacitor from the field of a rotating magnet and then discharge the capacitor to develop a high ignition voltage. Various types of coil arrangements are disclosed for performing charging and ignition functions. For example, the Foreman et al. U.S. Pat. No. 3,545,420 discloses arrangements in which two coils perform such functions, one coil serving as both a charging coil and as a secondary ignition coil and a second coil operating solely as a primary ignition coil through which the capacitor is discharged. In one arrangement, a trigger signal is obtained from a separate trigger coil and in another, a trigger signal isr obtained from the coil which serves as both the charging coil and the secondary ignition coil. The Burson U.S. Pat. No. 4,036,201 and the Burson U.S. Pat. No. Re. 31,837 disclose arrangement in which the charging and ignition functions are performed by three coils. A primary ignition coil, also serving as a trigger coil, is connected in series with an electronic switch and in parallel relation to a charging capacitor, while a charging coil is connected in series with a charging diode and in parallel relation to the charging capacitor. The charging coil and the primary and secondary ignition coils are located on the same leg of a core. To avoid a flux linkage between the charging coil and the ignition coils during ignition, the charging coil is magnetically separated from the primary and secondary ignition coils by providing a physical spacing of the coils on the core leg. The Phelon et al. U.S. Pat. No. 4,285,321 discloses an arrangement similar to that of the Burson patent in which the charging and ignition functions are performed by three coils and in which a trigger voltage is derived from the secondary ignition coil, rather than from the primary ignition coil. The Carlsson et al. U.S. Pat. No. 4,181,114 shows a four coil arrangement in which a charging coil is disposed on one outer leg of an E-shaped core, primary and secondary ignition coils are disposed on a middle leg of the core and a trigger coil on the the other outer leg of the core. The Carlsson et al. circuitry is unlike that of the Foreman et al. Burson and Phelon et al. patents in that a series circuit is formed by the primary coil, a capacitor, a diode and the charging coil. Isolation between the primary ignition coil and the charging coil is obtained by their location on separate core legs.
Various circuit features are incorporated in the systems of aforementioned patents and in those of other prior patents which relate to capacitor discharge ignition systems. For example, the aforementioned Foreman et al. patent discloses a protective device and a diode connected across the primary winding. The aforementioned Carlsson et al. patent discloses a varistor connected across a charging coil to limit the voltage thereacross and to protect a charging diode against an excessive inverse voltage. The Bodig U.S. Pat. No. 3,703,889 shows a reversing diode to prevent reverse charging of an ignition capacitor, and shows voltage divider circuitry connected to the gate of a thyristor used to dishcarge the capacitor. The Bodig patent also shows a voltage-dependent resistor across a charge coil. The Burson U.S. Pat. No. 3,955,549 and the Burson U.S. Pat. No. 4,033,311 show reverse-poled diodes across charging coils and the Anderson et al. U.S. Pat. No. 3,960,128 shows a reverse-poled diode across a a SCR. The Carmichael U.S. Pat. No. 4,056,088 shows a series circuit of a shunting diode and shunting resistor connected across a charging coil and the Carmichael U.S. Pat. No. 4,170,977 shows a diode connected across a charging coil. The Hohne et al. U.S. Pat. No. 3,500,809 shows a protective diode for assuring that only positive control signals are applied to the control electrode of an electronic switch. The aforementioned Foreman U.S. Pat. No. 3,545,420 also shows a diode for a similar purpose.
Arrangements such as disclosed in the prior art have been used commercially with some degree of success but have left much to be desired, particularly with respect to performance, relibility and cost of manufacture.